Protocols like RDP and ICA were not built to handle today's multimedia requirements. As desktop virtualization moves to the mainstream, this will have to change.

One negative aspect to being an early user of desktop virtualization software is that today's products use data delivery protocols built before end users demanded rich multimedia such as VoIP, IM and video.

Whether you are using thin client technology or one of the emerging desktop virtualization tools from Microsoft, Citrix Systems, VMware, Quest Software, Qumranet or another, each product uses a different protocol, which determines the performance of the multimedia as it is delivered to the desktop. Though many of the protocols are variants of Microsoft's Remote Desktop Protocol (RDP), which is built into Windows, performance of these individual protocols can vary substantially.

For corporations delivering remote desktops to end users in far-flung locations, this lack of predictability can be a problem, said David Payne, chief technology officer at Xcedex, a Minneapolis-based integrator that specializes in virtualization technology.

"The protocol deals with available bandwidth and it has a big responsibility," Payne said. "But bandwidth is unpredictable.

You may have high or low latency and that [protocol] has to perform well."

At his BriForum 2008 conference this week in Chicago, independent industry analyst Brian Madden details differences between many of the protocols in use today. The most common protocols are Microsoft's RDP and Citrix Inc.'s ICA (Independent Computing Architecture), which is a logical extension to RDP.

Citrix has enhanced ICA over the years, incrementally improving things like multimedia and microphone support. "One could argue that Citrix's prime business has been around ICA for 10 years, so naturally Citrix has improved ICA," Madden said.

Startup Qumranet Inc. has its own desktop virtualization software and a protocol called SPICE (Simple Protocol for Independent Computing Environments), built from scratch to handle multimedia. Madden said SPICE is "light years" ahead of ICA or RDP when it comes to support for VoIP, multimedia video and high-definition movies.

There is also a hardware-based technology called PC over IP, from Teredici Corp. Other vendors with virtual desktop technologies and their own protocols are Quest Software Inc., through its acquisition of Provision Networks, TCX from Wyse Technology Inc. and RGS from Hewlett-Packard. Quest and Wyse protocols are also logical extensions to Microsoft's RDP.

Why it is the way it is

Current desktop virtualization protocols are designed with the idea of server-based computing, explained Manlio Vecchiet, a group product manager in Microsoft's Windows Server marketing group. Processing and presentation is on the server, and the data sent to the client is simple visual images and keyboard strokes.

"Though the protocol to the desktop is important, historically there wasn't a lot of demand placed on the protocol because it processed simple applications minus rich graphics," Vecchiet said.

Also, because the nature of the work of those using traditional terminal services was such that those employees didn't need access to multimedia, the protocols were sufficient. What has changed now is with desktop virtualization. Server-based computing appeals to a broader range of users. Those individuals may need access to full streaming video or 3-D graphics, Vecchiet said.

Madden said exactly how or whether these vendors will alter their protocols to improve predictability and address deficiencies will be sorted out during the next few years.

Microsoft antes up with Calista

Beyond the mere improvement of existing protocols, there are some industry wild cards left to play. For example, Microsoft could tip its hand this week regarding its plans for the software it brought on board when it acquired Calista Technologies earlier this year. Calista had not yet shipped a product, but it was building an RDP-extension to deliver improved streaming features, support for 3-D applications and improve synchronization of audio and video on Windows desktops.

Calista's technology has both a client and server component. One of the functions of Calista is that it virtualizes Graphical Processing Units on a server so they can be used by different users. It also optimizes the capture of images so it can reduce the bandwidth, thereby reducing the number of bits that get passed down the pipe.

It's unclear whether or not the technology will become part of Hyper-V, Microsoft's built-in hypervisor, which is due out shortly.

The changing corporate desktop

There is also an effort underway to create a standard for desktop protocols. Driving this specification is the Video Electronic Standards Association, a non-profit organization that develops standards for PCs and consumer devices. The association's Net2Display spec has not yet been made public but it is supported by companies such as IBM and VMware.

Much will depend on how desktop virtualization technologies mature. Today, virtual desktops are not for everyone and most of the early products are still in their early stages. It's also possible that IT shops could make changes in their corporate desktop buying strategy, Madden said.

IT managers may also be thinking about skipping Microsoft Vista and jumping directly to Windows 7, which is scheduled to be out by 2010. By the time Windows 7 is available, IT shops may already be reconsidering how they deliver desktops to end users.

"This gives two years for the [virtual desktop]/protocol space to shake out and for VMware, Microsoft and Citrix to get their act together and decide what to do with [Virtual Desktop Integration]," Madden said. "This protocol discussion may be academic. In two years we could be in a different world."

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